If there is a hole in the street and you fall down it, you wouldn't expect a refund just for the 1 second it would have taken you to drive over that hole.

Instead you should be compensated for your losses - the time and money it took you to repair that tyre.

Same with a web service. If I pay for 24 * 7 service and it's not working when I go to use it, I want compensation for my time and effort resolving the matter.

For some that'll be small - eg. Searching Google instead, taking 30 seconds. For others it'll be a big headache.

But downtime of 1 hour is almost certainly more costly for the consumer than 1/30/24 * subscription price.